1. Field of the Invention
A magnetic sensing element, such as a tunneling magnetic sensing element, having an insulating film interposed between a laminate including a free magnetic layer and a bias layer disposed at each side in the track width direction of the laminate is provided.
2. Related Art
FIG. 11 is a partial cross-sectional view showing a conventional tunneling magnetic sensing element, taken in a direction parallel to the surface facing a recording medium (i.e., a surface parallel to the X-Z plane in the drawing).
A laminate 7 is disposed on a lower shielding layer 1, the laminate 7 including an antiferromagnetic layer 2, a pinned magnetic layer 3, an insulating barrier layer 4, a free magnetic layer 5, and a protective layer 6 disposed in that order from the bottom. The antiferromagnetic layer 2 is, for example, composed of a PtMn alloy, and the magnetization of the pinned magnetic layer 3 is pinned in the height direction (in the Y direction in the drawing) by an exchange coupling magnetic field produced between the antiferromagnetic layer 2 and the pinned magnetic layer 3.
The insulating barrier layer 4 is, for example, composed of Al2O3.
As shown in FIG. 11, first insulating films 8 are disposed at both sides in the track width direction (in the X direction in the drawing) of the laminate 7. Second insulating films 9 are disposed on the upper surface of the lower shielding layer 1 extending at both sides of the laminate 7 in the track width direction (in the X direction), the second insulating films 9 being connected with the respective first insulating films 8. Hard bias layers 10, for example, composed of a CoPt alloy are disposed on the respective first insulating films 8 and the respective second insulating films 9. Buried layers 11 are disposed on the respective hard bias layers 10. As shown in FIG. 11, an upper shielding layer 12 is disposed over the protective layer 6 and the buried layers 11. The lower shielding layer 1 and the upper shielding layer 12 also serve as electrodes, and a current flows through the laminate 7 in a direction parallel to the Z direction.
As shown in FIG. 11, the first insulating film 8 is provided to maintain insulation between the hard bias layer 10 and the laminate 7, and the second insulating film 9 is provided to maintain insulation between the hard bias layer 10 and the lower shielding layer 1.
Tunneling magnetic sensing elements are disclosed, for example, in Japanese Unexamined Patent Application Publication No. 2004-253437 (Patent Document 1) and Japanese Unexamined Patent Application Publication No. 10-162327 (Patent Document 2).
In the conventional tunneling magnetic sensing element, the thicknesses of the first insulating film 8 and the second insulating film 9 are not particularly controlled.
In order to ensure insulation between the hard bias layer 10 and the laminate 7 and between the hard bias layer 10 and the lower shielding layer 1, both the thickness T1 in the track width direction (in the X direction) of the first insulating film 8 and the thickness T2 of the second insulating film 9 are increased.
However, if the thickness T1 of the first insulating film 8 is excessively increased, the bias magnetic field supplied from the hard bias layer 10 to the free magnetic layer 5 is decreased, and it becomes difficult to properly align the magnetization of the free magnetic layer 5 in the track width direction (in the X direction).
If the thickness T1 of the first insulating film 8 is decreased, the problem described above is solved. However, if the thickness T2 of the second insulating film 9 is also decreased by the same extent as the thickness T1 of the first insulating film 8, short-circuiting more easily occurs between the hard bias layer 10 and the lower shielding layer 1 compared with between the hard bias layer 10 and the laminate 7, which is undesirable. The reason for this is that the area of the region in which the second insulating film 9 is formed is greatly larger than the area of the region in which the first insulating film 8 is formed, and the probability of the occurrence of pinholes and the like in the second insulating film 9 is higher than that in the first insulating film 8, thus increasing the occurrence of short-circuiting between the lower shielding layer 1 and the hard bias layer 10 through the pinholes.
As is evident with reference to FIG. 8, etc., of Patent Document 1, the first insulating films 8, the second insulating films 9, the hard bias layers 10, etc., are formed at both sides in the track width direction of the laminate 7 with a resist layer for lift-off processing (represented by reference numeral 71 in FIG. 8 of Patent Document 1) being placed on the upper surface of the laminate 7. However, when the resist layer for lift-off processing is used, if the first insulating film 8 is formed with a large thickness in the vicinity of an undercut portion (represented by reference numeral 71a of FIG. 8 in Patent Document 1), and in the worst case, if the inside of the undercut portion is filled with the insulating film 8, the resist layer cannot be lifted off. Therefore, as the first insulating film 8 is tapered upward (toward the end in the Z direction), the resist layer is more easily lifted off, which is preferable. However, if the first insulating film 8 is tapered upward, insulation between the laminate 7 and the hard bias layer 10 is degraded in the end portion, and as a result, short-circuiting easily occurs. In order to prevent the material of the hard bias layer 10 from entering the undercut portion when the hard bias layer 10 is deposited, it is preferable to control the deposition angle and the like during the deposition of the hard bias layer 10. However, this causes a problem of a decreased bias magnetic field supplied from the hard bias layer 10 to the free magnetic layer 5. Moreover, because of the shadow effect in which the sides of the resist layer produce shadowing, resulting in difficulty in film formation, the thicknesses of the first insulating film 8 and the hard bias layer 10 in the vicinity of the resist layer are further decreased.
Furthermore, if the thickness T2 of the second insulating film 8 is small, as shown in FIG. 11, the position of the hard bias layer 10 is lowered, and the thickest portions of the hard bias layers 10 tend to be located lower than both sides in the track width direction of the free magnetic layer 5. As a result, the bias layer supplied from the hard bias layer 10 to the free magnetic layer 5 tends to be decreased.